The present invention relates to gear synchronizer mechanisms for manual transmissions, and, more particularly, strut-type synchronizers adapted to prevent dislodgement of the strut members under centrifugal forces.
In general, conventional strut-type synchronizers include a plurality of key-like strut members which are normally biased into engagement with a circumferential detent groove formed in the internal spline surface of the clutch sleeve. Axial displacement of the shift sleeve causes the strut members to energize the synchronizer mechanism for blocking further axial displacement of the clutch sleeve until speed synchronization is complete. For example, U.S. Pat. No. 4,566,568 issued Jan. 28, 1986 to Yant discloses a strut-type synchronizer having a leaf spring member radially interposed between the hub and the clutch sleeve which is adapted to bias the strut members radially outwardly into engagement with the detent groove formed in the inner bore of the clutch sleeve.
U.S. Pat. No. 4,770,280 issued Sept. 13, 1988 to Frost and assigned to the common assignee of the instant application, discloses a strut-type blocking synchronizer mechanism which is incorporated into a vehicle transfer case for shifting from a two-wheel drive mode to a four-wheel drive mode of operation. The synchronizer mechanism includes a pair of energizing retainer springs acting to radially outwardly bias the strut members confined within slots in the hub into engagement with the detent groove.
The principle drawback associated with most conventional strut-type synchronizers however, has been their susceptiblity to becoming dislodged by centrifugal forces acting thereupon. It will be appreciated by those skilled in the art that conventional strut-type synchronizers are typically wider than "strutless" synchronizers since the clutch sleeve must support and retain the strut members within the hub upon full axial travel of the clutch sleeve into lock-up engagement with a speed gear or sprocket. However, it is desirable in most modern manual transmission and transfer cases to minimize the overall width of the synchronizer.